Receiving apparatus for electromagnetic waves



Jan. 10, 1928.

C. C. LAURITSEN RECEIVING APPARATUS FOR ELECTROMAGNETIC WAVES Filed May 9, 1925 INVENTOR m 04% ORNEY Patented Jan. 10, 1928.

um'rso STATES PATENT OFFICE.

CHARLES C. LAURITSEN, OF ST. LOUIS, MISSOURI, ASSIGNOR TO WAGNER EIIEGTRIC CORPORATION, OF ST. LOUIS, MISSOURI, A CORPORATION OF DELAWARE.

RECEIVING AIPPARATUS FOR ELECTROMAGNETIC WAVES. S Application filed May 9, 1923. Serial No. 637,641.

.Itis a well known fact that the simple by the drop of signal potential across the receiving apparatus now in common use in inductance is impressed upon the grid cir- 55 radio telephony, for example receiving sets cuit of the tube. This grid circuit may, as is of the single circuit type) lack, to a great common practice, include the grid condenser extent, the desirable property of selecting a 13 and grid leak 14. Filament current is desired signal to the exclusion of'signals of supplied from battery A controlled by rheov other-frequencies. Also a great deal of anstat 12. The plate circuit of the tube com- 60 noying interference with reception on nearprises battery B, telephones shunted by by receiving sets is caused by radiation from condenser 11, tickler coil 9 in inductive rela- 10 tube receiving sets when regeneration, or' tlon with coil 5, and the plate electrode 8 what is commonly known as the feed-back of the tube.' circuit is employed. 1 The circuits illustrated in Figure 2 differ 65 One of the ob'ects of this invention is tofrom those of Figure 1 only in that the secure sharp tuning and consequent elimitickler coil 9 is omitted from the plate cirnation or reduction of undesired signals and cuit and the grid circuit of the tube is other interference' by simple means requirconnected across the terminals of the caing minimum adjustments. pacity 4 of the closed oscillatory circuit in 70 A further object and advantage of the inthe collector systeminstead of across the vention is to prevent, or so decrease radiainductance 5'1 tion from tube receiving sets as to eliminate The circuits of Figure 3 correspond to interference between adiacently located sets. those of Figure 1 except in the omission of The objects of my invention are accomthe tickler coil 9 and the substitution of re- 75 plished without making it ncessary to desistance or inductance 15 for con-denser 3 part from the antenna height and dimenin the oscillatory circuit. J

sions most suitable for the collection of sufii- It will be understood that while, in the cient signal energy. drawings the detector circuit is shown di- In the accompanying drawings Figure 1 rectly connected to the collector system, one so diagrammatically illustrates receiving appaor more stages of amplification may be emratus of the regenerative type embodying ployed prior to detection, the grid circuit of my invention; Figure 2 illustrates a modithe first amplifying tube being connected to fication of the arrangement shown in Figthe collector system in the same manner as ure 1, regeneration being omitted, and Figthe detector circuits are connected in the g5 ure 3 shows another modification, also withillustrations. out regeneration. The elements of the closed oscillatory cir- Referring toFigure 1 the collector syscuit in the collector system are proportioned V tern comprises'the antenna 1 and ground to produce a stiff circuit, the resistance beconnection 2, which are connected as shown ing low and the ratio of inductance to ca-' to a closed oscillatory circuit comprising the pacity being high. A suitable value for the condenser 3 of comparatively'large capacity, inductance is 250 milli-henrys, and that for 40 the condenser 4, and the inductance 5. As condenser 3 is .001 microfarad. The cashown, the connections of the antenna and p'acity of condenser 4 is variable and a suitground to this closed oscillatory circuit are able maximum value is .0003 microfarad. so located that the circuit has two branches The value normally employed will of course between the antenna and ground connecbe less than the maximum, and it is pref- 45 trons, one containing the capacity 3,.and erable that the maximumcapacity of 4 be which is hereinafter referred to asthe byless than that of 3.

pass branch, and the other the capacity 4 By adjustment of the variable condenser and inductance 5, hereinafter referredto as 4, or the inductance 5, or both, the oscillathe signal receiving branch. torycircuit is rendered resonant t0 the de- 50 The vacuum tube T has its'grid electrode sired signal wave length and is capable of 6 and filament'electrode 7 directly connected vbeing made resonant to what are usually re-- to points on the signal receiving-circuit on ferred to as short wave lengths, that is to opposite sides of the inductance 5, wheresay, of 600 meters and shorter. Being a 'resista'nce to higher frequencies, such as 200 meter spark waves and certain types of static.

When regeneration 1s employed as 1ndicated in Figure 1 only a small ortion of the oscillatory energy produce will be radiated from the antenna, on account of the fact that the generated E. M. F. is so distributed in the oscillatory circuit that only a small part of same is impressed between the antenna and ground. This is due to the fact that the capacity of condenser 4 is in series with the parallel combination of the antenna to ground capacity and the capacity 3. The capacity of this parallel combination is high compared to the capacity of the condenser 4. The total E. M. F. in the oscillatory circuit (whether produced by regeneration or not) is always divided between these capacities in series, and since this division is in inverse proportion to their values, the E. M. F. applied between antenna and ground will be only a small fraction of the total E. M. F. in the circuit. The amount of energy radiated from the antenna will, therefore, be proportionately small, and as this is equivalent to reducing the radiation resistance, the selectivity of the system is improved. Tests have shown that the amount of energy radiated from my receiving apparatus is less than onefifteenth as great as that radiated under similar conditions. by the ordinary single circuit regenerative receivers. The result is that receiving apparatus constructed in accordance with my invention will not create the disturbing beat-note and other noises in near-by receiving sets even though it is used with regeneration and even with the tube oscillating.

It will be understood that the connection of the antenna and ground to the closed circuit results in there being the equivalent of a capacity in parallel with capacity 3, so far as tuning is concerned, and will very slightly influence the tuning, and that where'referonce is made in the description and claims to adjusting the closed oscillatory circuit to resonance with signals of the frequency to be received, I mean that the elements of this circuit are so adjusted that in cooperatipn with the above factor a tuned system is produced which is resonant to signals of the frequency to be received. In other words, this antenna to ground capacity constitutes a part of the capacity of the closed oscillatory circuit from the standpoint of the tuning referred to.

I am aware that modifications in the type of capacit and other elements herein illustrated an described may be made without departing from my invention and I do not therefore intend that its scope be limited otherwisethan by the appended claims.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. Receiving apparatus for electromagnetic Waves comprising a collector circuit and a closed oscillatory circuit connected in the collector circuit in such manner that one portion of the oscillatory circuit constitutes a by-pass branch, and the other portion a signal receiving branch, the by-pass branch containing impedance, and the signal receiving branch containing inductance and capacity elements adjusted to render the oscillatory circuit resonant to signals of the frequency to be received, the impedance of the capacity element of the signal receiving branch to said signal current being of higher value than the impedance in the by-pass branch, and means associated with the signal receiving branch for detecting the received signals.

2. Receiving apparatus for electromagnetic waves comprising a collector circuit and a closed oscillatory circuit connected in the collector circuit in such manner that one portion of the oscillatory circuit constitutes a by-pass branch and the other portion a signal receiving branch, the by-pass branch containing impedance, and the signal receiv ing branch containing inductance and capacity elements adjusted to render the oscillatory circuit resonant to signals of the frequency to be received, the.impedance of the capacity element of the signal receiving branch to said signal current being of higher value than the impedance in the by-pass branch, andva signal amplifying or detecting circuit connected to points on the signal receiving branch between which there is a difference of signal potential.

3. Receiving apparatus for electroma g -f netic waves comprising a collector circuit and a closed oscillatory circuit connected in the collector circuit in such manner that one portion of the oscillatory circuit constitutes a by-pass branch and the other portion a signal receiving branch, the signal receiving branch containing inductance and capacity elements adjusted to render the oscillatory circuit resonant to signals of the frequency to be received, and the by-pass branch being constituted to offer to waves of frequencies other than the frequency to be received a lower impedance path than exists' through the signal receiving branch, and means associated with the signal receiving branch for detecting the received signals.

4. A receiving apparatus for electromagnetic waves comprising an antenna, a closed oscillatory circuit comprising an inductance, a condenser and an impedance all in series, said closed circuit being connected to the antenna at a point between the condenser and said impedance and to ground at a point between the inductance and said impedance, whereby a collector circuit is formed comprising a signal receiving branch containing the inductance and the condenser and a by-pass branch containing the impedance, the impedance of the by-pass branch to said signal currents of any frequency within the receiving range of the apparatus being of lower value than the impedance to said signal current offered by the combination of the antenna to ground capacity and the capacity of the condenser in the signal receiving branch, and signal receiving means associated with the signal receiving branch. 5. A receiving apparatus for electromagnetic waves comprising an antenna, a closed oscillatory circuit comprising an inductance, a condenser and an impedance allin series, said closed circuit being connected to the antenna at a point between the condenser and said impedance and to ground at a point between the inductance and said impedance, whereby a collector circuit is formed comprising a signal receiving branch containing the inductance and the condenser and a by-pass signal receiving branch, said means comprising a device capable of producing electrical oscillations in the aforesaid closed oscillatory circuit.

In testimony whereof, I have hereunto set my hand.

CHAS. C. LAURITSEN. 

